Concentration of sylvite ores



Patented Sept. 21, 1954 CONCENTRATION OF SYLVITE ORES George E. Atwood,Carlsbad, N. Mex., assignor to International Minerals & ChemicalCorporation, a, corporation of New York No Drawing. Continuat cationSerial No. 696, This application M 8 Claims.

This invention relates to the concentration of sylvite ores and is ofparticular value in connection with the separation of sylvite from oresof the sylvinite type, for example such ores as are found in theCarlsbad district of New Mexico, U. S. A. The invention has beensuccessfully employed in the concentration of the sylvinite oresproduced from that part of the Carlsbad field which is mined byInternational Minerals and Chemical Corporation.

The typical analysis of such ore is as follows:

Per cent Sylvite (KCl) 31 Halite (NaCl) 65 Other constituent orimpurities consisting of silicates, sulphates, etc 4 This invention isof particular value in con.- nection with processes of the general typedis.- closed in the Tartaron, Cole and Duke Patent No. 2,288,497. Saidpatent describes a process which comprises suspending comminutedsylvinite ore in a circulating saturated brine formed by dis solving thesoluble constituents of the ore in water and then floating the particlesof sylvite in the brine by means of a suitable collector agent whilepermitting the particles of halite to settle. The type of process towhich this invention relates i thus distinguished from that type ofprocess disclosed in the Weinig Patent No. 2,222,331, issued November19, 1940, in which the halite is floated and the sylvite is settled.

In processes of this general character, it had been the general practiceto grind the ore to a rather fine mesh, for example, in a good manycases, to a degree of fineness where at least 9.0% of the ore would passthrough a sieve of about 40 mesh. Flotation of the. valuableconstituents of an ore of such degree of fineness is not too difficult aproblem, and various types of collector agents for efiecting suchflotation can be used. However, a concentrate in which the particles areof extremely fine size is not easily handled. There is more caking instorage in the shipping container than in the case of particles ofrelatively larger size, andin general it maybe said that a fertilizeringredient in the form of fine powder is not as desirable as a materialwhich occurs in the form of relatively large crystals. Furthermore, theexpense of fine grinding is rather considerable and adds materially tothe cost of the final product.

It may be stated as a general propositionthat the flotation of oreconsisting of relatively large particles is attended with considerablymore ion of abandoned appli- 933, September 18, 1946. ay 15, 1952,Serial No.

difiiculty than in a case where the particles are of relatively smallerdimensions. Furthermore, there are so many problems and so manyvariables in a flotation plant that it is an extremely difficult mattersometimes to determine just what is the trouble with the system when afalling off in the recovery or purity of product is observed, andsometimes because of the character of the operation a falling off inrecovery or quality is not noticed until after the condition causing thepoor result has disappeared and perhaps totally different conditionshave developed in connection with other variables in the system. Thus,it wili be seen that there are three factors involved in the cure of abad result:

First, the bed result must be observed at the precise time when thesystem is producing a bad result.

Second, the conditions existing at the time of the bad result must beaccurately and promptly ascertained.

Third, which one or two or more of the variable conditions areresponsible for the bad result, and how should these variables beadjusted in order to obtain an optimum result.

I have discovered that in the concentrating of sylvinite ore to obtain arelatively coarse concentrate, for example, one in which the particlesof sylvite are of such size that 50% of the material will be retained ona 40 mesh sieve, an overthe-year orannual loss in recovery or quality ofproduct, or both, is caused by a variation in the temperature of thecirculating brine. In some cases, when the temperature rises to say, 40(3.,

wh h. it s m times does the Carl bad district.

the recovery often falls .01? very much as compared with the recoveryunder apparently. the same condition at a brine temperature of 25 C.,whereas, in the cold winter weather when the brine temperature may be aslow as 10 C., the percentage of recovery is often found to be much lowerthan it was at 25 C., brine temperature. Apparently, with all otherconditions equal, there seems to be an optimum temperature for the bestrecovery. This would suggest that steps should be taken to maintain thetemperature of the brine at the optimum temperature. But, unfortunately,the capital expense and the operating expense for maintaining a constantbrine temperature is prohibitive at a place like Carlsbad, New Mexico,where the air temperature may range from I.) F., in the winter to ashigh as F., in the middle of summer, and where a large part of thesystem equipment is located out 3 of doors or is subject to out-doorweather conditions.

I have found that in the treatment of an ore such as has been describedand of coarse particle size the best average results have been obtainedwith a collector agent selected from the class of primary aliphaticamines and their acid addition salts, preferably the acetates orhydrochlorides. The chain length apparently should be predominantlyequivalent to about C18. Compounds with a greater chain length, e. g.,C20, and a higher melting point may be used but are not generallyavailable, while compounds with a shorter chain, e. g., C14 and a lowermelting point do not appear to work so well except at much lower brinetemperatures. A typical analysis of asatisfactory collector is:

Double Bonds Percent Compound I have made the surprising discovery thatwith collector agents of an average chain length within the rangebetween C16 and C20, which appear to give fair results with fineparticle size pulp, and give inferior average results with coarser pulp,the results can be materially improved by varying the degree ofunsaturation (average number of double bonds in the chain) in accordancewith variations in the brine temperature. The higher the temperature ofbrine, the lower should be the degree of unsaturation, i. e., theaverage number of double bonds in the chain should be reduced.

The reduction in unsaturation of iodine value can be accomplished byselection of the various fatty acids or combinations of same from whichthe amine or amines are made, or by a hydrogenation step. In general,working under the conditions and with the materials indicated, it isfound to be satisfactory to operate with a saturation range extendingbetween an iodine value of about 150, which is roughly equivalent toabout one and one-half double bonds in the chain, down to an iodinevalue or double bond equivalent of about 0. This range will accommodatebrine temperatures between about C., and 40 C. With lower temperaturesthan 10 C., a reagent with a somewhat higher double bond equivalent oriodine value or a reagent with a somewhat shorter average chain lengththan C18 is indicated, although complete data in respect of actual testruns at temperatures lower than 10 C., are not yet available.

The effect of varying amounts of unsaturation when using a collectorreagent having a chain of approximately C18 is shown by the followingactual flotation tests.

The particle size of feed material (sylvinite ore) was as follows:

Per cent Particle size larger than 20 mesh i- 8.35 Particle size largerthan 35 mesh 44.80 Particle size larger than 80 mesh 80.53 Particle sizeless than 80 mesh 19.47

The collector used had a chemical analysis sub stantially the same asthat stated previously. The only variables in the various tests were thetemperatures and degree of unsaturation or number of double bonds. About.35 pound of the 4 amine collector was used for each ton of feed, and inaddition thereof, the amount of corn starch added was about 1.25 poundsper ton of feed. The general proces was substantially as set forth inthe Tartaron, et al. Patent No. 2,288,497, previously referred to. Thestarch is added to the closed system preferably at a high point ahead ofthe stage where the primary collecting agent is introduced into thesystem. It is preferably used in the form of a dispersion in brine madeby boiling 3% of dry starch in about 97% of brine. About 0.20 pound ofpine oil per ton of feed is added to the system at any convenient pointbefore the pulp reaches the flotation cells. The pulp fed to the cellscontains 30% of solids by weight.

The results at various temperatures in a single flotation operation whenusing a collector of the same average chain length (about C18) buthaving different degrees of saturation are shown in the following table:

Saturation Double Pulp Temp. g i I2 Value Feed Tails Cone. Recoveryalent A collector agent consisting of a single compound could be used ifits degree of saturation and its chain length happened to fit theconditions existing. However, since the saturation of individualcompounds cannot differ by less than one double bond, it is usuallyconvenient to use combinations of different compounds in order to obtainthe average saturation and chain length required. Further tests at anintermediate temperature of 18 C. indicate that an optimum recovery wasobtained when the double bond equivalent was about 1.0 with an iodinevalue of approximately 90. The recovered material when cleaned andre-cleaned according to improved flotation procedure was of high purity,containing more than 61% K20 equivalent. ,7

When employing the described collector agent for the flotation ofrelatively coarse material of the kind referred to, I have found thatthere is considerable economy effected in consumption of reagent,because it is possible to obtain a satisfactory flotation effect by theuse of considerably less collector agent. Since these collector agentsare fairly expensive, any saving in this respect will be reflected inthe cost of production of concentrate I have also discovered that it ispossible to effect a further increase in recovery or to employ a stillcoarser feed than indicated, or to accomplish both of these desirableresults, if there be present in the brine system in addition to theamine collector a minute quantity, preferably not more than about 50parts per million, of a metallic salt which is soluble in the brine. Ihave found that these results can be obtained by the use of an amount ofsuch salt which will maintain in the brine a concentration equivalent toabout 10 parts by weight of salt to 1,000,000 part by weight of brine.The particular salts with which I have had best results are thebrine-soluble salts of lead or other metals such as bismuth or silver.The acetates, chlorides, etc., of these metals, which are brine soluble,may be employed.

This application is a continuation of application Serial No. 696,933,filed September 13, 1946, and now abandoned.

I claim:

1. In a process for separating sylvite from sylvinite ore by firstpulping the comminuted ore in an aqueous brine saturated with respect tothe ore under the conditions obtaining, and then floating ofi sylvite bysubjecting the pulp to-a flotation step involving the use of acollecting agent containing a mixture of alkyl and alkenyl aminecomponents selected from the group consisting of primary aliphaticamines containing long straight chain hydrocarbon groups and their Watersoluble acid addition salts where the flotation step is carried out overa period of time during which the temperature of the flotation pulpchanges, the improvement comprising maintaining the flotation efliciencyof the collecting agent by first selecting an amine mixture which hasbeen found to give optimum results at one temperature and then changingthe relative amount of the alkyl and alkenyl components of the aminemixture in accordance with changes of temperature of the flotation pulpso as to reduce the iodine number in accordance with an increase intemperature and increase the iodine number in accordance with a decreasein temperature.

2. In a process for separating sylvite from sylvinite ore by firstpulping the comminuted ore in an aqueous brine saturated with respect tothe ore under the conditions obtaining, and then floating oil sylvite bysubjecting the pulp to a flotation step involving the use of acollecting agent containing a mixture of alkyl and alkenyl aminecomponents selected from the group consisting of primary aliphaticamines containing long straight chain hydrocarbon groups and their watersoluble acid addition salts where the flotation step is carried out overa period of time during which the temperature of the flotation pulpchanges within the range between about and about 40 C., the improvementcomprising maintaining the flotation efllciency of the collecting agentby first selecting an amine mixture which has been found to give optimumresults at one temperature within said temperature range and thenchanging the relative amount of the alkyl and alkenyl components of theamine mixture in accordance with changes of temperature of the flotationpulp so as to reduce the iodine number in accordance with an increase intemperature and increase the iodine number in accordance with a decreasein temperature within the range between about 10 C. at which temperaturethe iodine number is about 150 and about 40 C. at which temperature theiodine number is just above zero.

3. A process as in claim 1 wherein the primary aliphatic amines employedhave 16 to carbon atoms, inclusive, per molecule.

4. A process as in claim 2 wherein the primary aliphatic amines employedhave 16 to 20 carbon atoms, inclusive, per molecule.

5. In a process for separating sylvite from sylvinite ore by firstpulping the comminuted ore in an aqueous brine saturated with respect tothe ore under the conditions obtaining, and then floating off sylvite bysubjecting the pulp to a flotation step involving the use of acollecting agent containing a mixture of alkyl and alkenyl aminecomponents selected from the group consisting of primary aliphaticamines containing long straight chain hydrocarbon groups and theirwater-soluble addition salts, the improvement comprising maintaining theflotation efliciency of the collecting agent over a period of timeduring which the temperature of the flotation pulp changes in the rangeof between about 10 C. and 40 C., by changing the composition of thecollecting agent with respect to the relative amount of the alkyl andalkenyl components from one composition having an iodine number justabove zero when the pulp has a tempertaure of about 40 C. to acomposition having an iodine number of about 45 when the pulphas atemperature of about 25 C. and to a composition having an iodine numberof about when the pulp has a temperature of about 10 C.

6. A process as in claim 5 wherein the primary aliphatic amines employedhave 16 to 20 carbon atoms, inclusive, per molecule.

7. In a process for separating sylvite from a sylvinite ore by firstpulping the comminuted ore in a brine saturated with respect to the oreunder the conditions obtaining, and then floating oif sylvite bysubjecting the pulp to a flotation step involving the use of acollecting agent containing amine substances selected from the groupconsisting of primary aliphatic amines containing a straight chainhydrocarbon group having from 16 to 20 carbon atoms inclusive, and theirwatersoluble acid addition salts, the improvement comprising, employinga collecting agent comprising a mixture of said amines, at least some ofthe amine constituents of which contain alkenyl, the iodine number ofthe amine mixture being about 135, with the brine temperature beingabout 10 C.

8. In a process for separating sylvite from a sylvinite ore by firstpulping the comminuted ore in a brine saturated with respect'to the oreunder the conditions obtaining, and then floating oif sylvite bysubjecting the pulp to a flotation step involving the use of acollecting agent containing amine substances selected from the groupconsisting of primary aliphatic amines containing a straight chainhydrocarbon group having from 16 to 20- carbon atoms inclusive, andtheir watersoluble acid addition salts, the improvement comprising,employing a collecting agent comprising a mixture of said amines, atleast some of the amine constituents of which contain alkenyl, theiodine number of the amine mixture being about 45, with the brinetemperature being about 25 C.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,211,396 Weinig Aug. 13, 1940 23 Cole Dec. 26, 1944

1. IN A PROCESS FOR SEPARATING SYLVITE FROM SYLVINITE ORE BY FIRSTPULPING THE COMMINUTED ORE IN AN AQUEOUS BRINE SATURATED WITH RESPECT TOTHE ORE UNDER THE CONDITIONS OBTAINING, AND THEN FLOATING OFF SYLVITE BYSUBJECTING THE PULP TO A FLOTATION STEP INVOLVING THE USE OF ACOLLECTING AGENT CONTAINING A MIXTURE OF ALKYL AND ALKENYL AMINECOMPONENTS SELECTED FROM THE GROUP CONSISTING OF PRIMARY ALIPHATICAMINES CONTAINING LONG STRAIGHT CHAIN HYDROCARBON GROUPS AND THEIR WATERSOLUBLE ACID ADDITION SALTS WHERE THE FLOTATION STEP IS CARRIED OUT OVERA PERIOD OF TIME DURING WHICH THE TEMPERATURE OF THE FLOTATION PULPCHANGES, THE IMPROVEMENT COMPRISING MAINTAINING THE FLOTATION EFFICIENCYOF THE COLLECTING AGENT BY FIRST SELECTING AN AMINE MIXTURE WHICH HASBEEN FOUND TO GIVE OPTIMUM RESULTS AT ONE TEMPERATURE AND THEN CHANGINGTHE RELATIVE AMOUNT OF THE ALKYL AND ALKENYL COMPONENTS OF THE AMINEMIXTURE IN ACCORDANCE WITH CHANGES OF TEMPERATURE OF THE FLOTATION PULPSO AS TO REDUCE THE IODINE NUMBER IN ACCORDANCE WITH AN INCREASE INTEMPERATURE AND INCREASE THE IODINE NUMBER IN ACCORDANCE WITH A DECREASEIN TEMPERATURE.